The present invention relates to carrying out a handover in a mobile data transmission system, with data being passed on at least partially on the basis of the Internet Protocol (IP) in the mobile data transmission system. At least some of the devices in the data transmission system are thus connected to one another by an IP network. Packet-data-based data transmission therefore takes place at least in a subarea of the data transmission system. A connection such as this by an IP network is in principle known from the related art. As an example of this, reference should be made to WO 98/38808.
However, other possible ways for connecting the devices in a mobile data transmission system are known, such as those which are used in the mobile radio systems that exist at the moment. In this case, the devices are connected to one another by means, for example, of ATM networks or PCM30 lines.
However, the present invention is not just restricted to mobile radio systems such as these. For example, it can in principle be used for different types of mobile data transmission systems which may be designed to transmit any desired data such as multimedia data, speech data, data from computer networks or the like.
The systems and methods which are well known from the related art for carrying out a handover have the disadvantage that a high level of complexity is required in order to pass on the data within the mobile data transmission system. In particular, it is possible in previous systems and methods for a situation to arise during a handover from a first transmitting/receiving device to a second transmitting/receiving device in which, although a mobile terminal is supplied from the second transmitting/receiving device during and after a successful handover, the data stream from the data transmission system to the terminal still has to be passed via the first transmitting/receiving device however, in order to ensure a continuous data stream. In cases such as this, considerable complexity is involved in changing the route for passing on data within the data transmission system. In addition, in a packet-data-based network, the process of setting up the connection from the second transmitting/receiving device to the mobile terminal can actually take a relative long time lasting up to several seconds, which is not acceptable for providing real-time communications connections such as speech or multimedia connections in data transmission systems such as these.
A. O'Neill et al., “Edge Mobility Architecture”, Internet Draft, July 2000, XP002169893, describes handover scenarios for an edge mobility architecture (EMA). In this case, a connection is set up between an old access router (OAR) and a new access router (NAR) during a handover. Data can be transmitted from the old access router to the new access router via this connection. Two variants of the procedure for a handover are described. On the one hand, the connection to the old access router can be interrupted before the connection to the new access router exists, or on the other hand the connection to the old access router is interrupted only after the connection to the new access router has been terminated.
G Eneroth et al., “Applying ATM/AAL2 as a switching technology in third-generation mobile access networks”, IEEE communications magazine, IEEE service center Piscataway, N.J., US, Volume 37, No. 6, June 1999, pages 112–122, XP000835287 ISSN: 0163-6804, describes a soft handover in a third-generation mobile communications system which uses ATM (asynchronous transfer mode).
A. G. Valko, “Cellular IP: A new approach to Internet host mobility”, Computer Communications Review, Association for Computer Machinery, New York, US, Volume 29, No. 1, January 1999, pages 50–65, XP000823873 ISSN: 0146-4833, describes an IP-based mobile communications system, in which the data in the downlink direction is transmitted to the old base station and to the new base station during a handoff which is initiated by a mobile terminal.